High-precision Monitoring Method for Extrusion Displacement Field of Tunnel Face Based on 3D Laser Point Cloud
To achieve rapid,automated,and high-precision overall monitoring of the tunnel face,a method based on three-dimensional(3D)laser point clouds is proposed to monitor the tunnel face extrusion displacement field.This includes a simple and highly accurate rigid-body reference introduction method and nonrigid face deformation path-tracking technology for the tunnel.First,a stable rigid-body reference based on the initial support longitudinal direction was proposed based on the assumption of plane strain.The wave characteristics of the initial support were expressed based on two-dimensional continuous wavelet transform,assuming a local small-deformation rigid body.A multilevel iterative registration algorithm was applied to correct the position of the initial support and achieve rigid body reference registration.Finally,the point-cloud normal vector clustering algorithm was used to segment the tunnel face.Based on the assumption of a small local deformation rigid body,the path-tracking algorithm was used to obtain the displacement path of each tunnel face,resulting in the extrusion displacement field of each tunnel face.The results of this study were experimentally verified in highway tunnels.The tunnel face extrusion displacement estimated using the proposed method,was qualitatively compared with that obtained with and without deformation path tracking under traditional rigid body reference.In addition,a quantitative comparative analysis was conducted using the extrusion results monitored by the total station.The results indicate that the research findings of this study can accurately monitor the extrusion displacement field of the tunnel face,and the root mean square error with respect to total station monitoring was 0.83 mm.The results of this study can be used to monitor and analyze the stability of the tunnel face and effectively warn of geological disasters,thereby improving the safety of the tunnel excavation process.
tunnel engineeringdisplacement field monitoringtwo dimensional continuous wave-let transformthree dimensional laser scanning technologystable rigid body reference